Rotary regenerative heat exchangers

ABSTRACT

A rotary regenerative air preheater is provided a linkage for adjusting the positions of movable and spring-biased sealing plates or strips relatively to the matrix. In this linkage is included a hydraulic servo motor governed by impulses from means sensing changes of the length of the linkage caused by a foreign body or the like passing between a sealing element and the matrix and forcing the sealing element away from the matrix. At such occasions the servo motor is actuated to move the sealing element further away from the matrix to allow the passage of the foreign body whereby damage is avoided.

D United States Patent [is] 3,669,183 Mock 145 1 June 13, 1972 4] ROTARY REGENERATIVE HEAT [56] References Cited EXCHANGERS UNITED STATES PATENTS [72] Inventor: Karl Helnz Mock. Neckargemuend, Ger- 3,232,335 2/1966 Kalbfleisch "165 /9 many 3,404,727 10/1968 Mock ..l65/9 I73] Assignee: :vens'lm Rotor Masklner Alitiebolag, primary Examiner Alben w Davis" JR Sweden Attorney-Bauer and Goodman [22] Filed: Aug. 26, 1970 [57] ABSTRACT [21] App]. No.: 66,954

A rotary regenerative air preheater |s provided a linkage for adjusting the positions of movable and spring-biased sealing g pp y plates or strips relatively to the matrix. In this linkage is included a hydraulic servo motor governed by impulses from Sept Germany 19 485'4 means sensing changes of the length of the linkage caused by a 52] U S Cl 165/9 foreign body or the like passing between a sealing element and [5]] ln.t.cl the matrix and forcing the sealing element away from the l 5 8 Fie'ld 1 /9 matrix. At such occasions the servo motor is actuated to move the sealing element further away from the matrix to allow the passage of the foreign body whereby damage is avoided.

11 Claims, 4 Drawing Figures I 5 a 7 f I I I I II I i I 7 5 a I 4 l0 1 ROTARY REGENERATIVE HEAT EXCHANGERS The invention relates to rotary regenerative heat exchangers and concerns the adjustment of the clearance between the end surfaces of the matrix and the sealing elements separating the flows of heat exchanging fluids. This clearance must be as small as possible but direct contact between relatively movable sealing surfaces must be avoided to the utmost possible extent in order to prevent rapid wear of the surfaces due to the grinding action at a sliding contact.

The solution of this problem is difficult due to the fact that the matrix is subject to thermal deformation during operation. In addition, the surfaces of the matrix may also become irregular for unforeseeable reasons for instance such that foreign bodies fall down on the matrix and are carried around by the matrix, the foreign bodies being for example, internal duct struts, articles used at the assembly and left behind and forgotten or other foreign elements. Such elements may cause friction and even come into severe collision with the sealing elements resulting in rapid wear and damage.

For this reason several solutions have already been suggested and put into practice permitting a rapid and sufiicient increase of the initially correctly adjusted clearance when a disturbance of the type described arises. When the disturbance has been eliminated the normal clearance can be reestablished. For instance, in German Patent Specification No. 1,045,032 there is shown a quick-release device for rapid withdrawal of a sealing element which runs the risk of being damaged. Such a device functions satisfactorily in practice but has the disadvantage that the supervising persons have to leave the central and go to the preheater in order to inform themselves of the disturbance and its proportions, even though the device of course may be remotely controlled.

There are also known rapidly operating hydraulic servo devices which at disturbances increase the clearance by a predetermined amount (US. Pat. No. 3,404,727). Both of these solutions have the disadvantage that the large clearance remains also after the elimination of the disturbances so that the normal clearance width must be re-established manually.

Another known device operates automatically by sensing the surface of the matrix and adjusting the sealing element in response to impulses from the sensing member of the device (US. Pat. No. 3,232,335). However, the constructive nature of this device is such that only a relatively low number of sensing members can be provided. It is therefore not possible to make the device such that it detects also local irregularities of the matrix surface for instance caused by foreign bodies.

SUMMARY OF THE INVENTION According to the present invention there is provided a new way to solve the problem to adjust the sealing device in response to deformations of the matrix surface while obviating the drawbacks of known devices. The device according to the present invention which thus serves to actuate the sealing plates or sealing strips of rotary regenerative air preheaters is made such that it withdraws the sealing elements also when separate foreign bodies are encountered and automatically reestablishes the original clearance width as soon as the disturbances have been eliminated.

As distinguished from known devices the device according to the invention is characterized by a hydraulic servo motor of the piston/cylinder type which is included in an adjusting linkage such that it determines the effective length thereof, a spring counter-acting said servo motor, means first sensing sensing changes of the effective length of the linkage or of the position of the piston second sensing means sensing the hydraulic pressure in the inlet of the servo motor, and a valve in the inlet conduit which is altematingly opened and closed in response to impulses from the first sensing means, the valve being independently opened by the second sensing means when the pressure in the servo motor inlet falls below a predetermined value.

The invention will now be explained with reference to two embodiments thereof shown in the accompanying drawing.

FIG. 1 is a cross-section of an air preheater having a rotating matrix and stationary ducts and in which coaxially aligned sector plates are interconnected by an adjusting device according to the invention;

FIG. 2 shows on a larger scale a servo motor and elements appertaining thereto comprised in the adjusting device and forming the essential part thereof;

FIG. 3 is a plan view of the preheater in FIG. I and illustrates the invention as applied to an axial sealing plate cooperating with the outer peripheral wall of the matrix; and

FIG. 4 shows a partial sectional view of an alternative embodiment of the servo motor of FIG. 2.

For illustration of the invention, an air preheater having a rotating matrix or regenerator body and stationary ducts has been selected because this type of preheater is the most frequently used one. However, the invention is also applicable to heat exchangers having a stationary matrix and rotating duct connections. The preheater shown has a housing 1 in which the matrix 2 is rotatably joumaled in bearings 3 and 4 in a known manner. In order to sealingly separate the air and gas flows from each other there are provided sector plates 5 and 5 at the end surfaces of the matrix and at the outer peripheral wall of the matrix there are also axial sealing plates 6.

FIG. 1 shows the adjusting device which interconnects the axially aligned sector plates 5 and 5. The connection includes a plurality of rods pivotally connected with each other. Rods 7 and 7' are connected to the sector plates or sections thereof and to these rods are connected bell cranks 8 and 8', horizontal rods 9 and 9', bell cranks l0 and 10' and coupling rods 11 and 11 connected to an interposed servo motor device 12 of the piston/cylinder type. It is evident that the two coupling rods 11 and 1] are moved away from each other when a sector plate is forced away from the matrix by a foreign body or by a deformed portion of the matrix protruding from the matrix surface and passing across the sector plate.

The servo motor device 12 is shown in FIG. 2 on a larger scale and comprises a preferably cylindrical housing 13 en closing the servo motor cylinder 30. The servo motor piston 33 may have a diameter slightly smaller than the inner diame ter of the cylinder 30 resulting in a small clearance between the piston and the cylinder wall or the piston may be provided with a'(such as bore 28 of FIG. 4) bore or the like so that in case of different pressures in the two cylinder chambers the pressure oil leaks over from one chamber to the other. The piston rod 34 carries a spring seat 14 for one end of a compression spring 15 provided in the upper portion of the housing 13. Inside the housing 13 there are provided abutments 35 which limit the expansion of the spring such that the spring is still under a certain compression when the seat 14 rests on the abutments 35. This pre-compression must be so high that it under normal conditions prevents separation of the coupling rods 11 and 11'. A compression of the spring 15 must not take place except in case of disturbances for instance produced by foreign bodies carried around by the matrix and forcing a sector plate outwardly when passing the same.

The bottom of the servo motor cylinder 30 is connected to the bottom of the casing 13 and consequently also with the coupling rod 11 while the piston rod 34 with the spring seat 14 is connected to the coupling rod -1 1. To the coupling rod 1 l is secured a rectangularly bent rod 16 which carries a plurality of cams l7. Adjacent to the path of movement of the earns 17 there is a switch 18 which is passed by the cams when the coupling rods 11 and 11' are forced apart and the spring 15 is compressed.

Pressure oil is supplied to the lower working chamber of the servo motor from a pressure vessel or an oil pump through a supply conduit 31 which is provided with a valve 37 and a pressure switch 36. The other chamber of the servo motor is drained through a conduit 32 leading to a sump.

When the air preheater is out of operation the spring seat 14 is held against the abutments 35 by the spring 15. This will also be the case if the oil pressure system fails.

When the preheater is started the oil pump starts running building up a pressure in the supply conduit 31 upstream of the valve 37. Initially the switch 18 is engaged by an abutment 17u secured to and limiting downward movement of the rod 16. When actuated in this manner the switch 18 opens the valve 37 so that pressure oil enters the lower working chamber of the cylinder 30. When the piston then moves upwardly the spring seat is raised from the abutment 35, but when the cam 17 engages the switch 18 the latter will cause the valve 37 to close. In this manner oil is trapped within the lower working chamber at a pressure dependent on the compression of the spring 15.

As mentioned above there is a desired leakage across the piston and therefore the piston 33 starts to descend slowly towards its initial position. Due to the action of the spring the pressure in the chamber below the piston 33 does not change to any appreciable extent during this movement of the piston and therefore the pressure switch 36 remains inoperative. If the limit abutment l7u reaches the switch 18 the valve 37 is again opened and the piston will again move upwardly until the cam 17 engages the switch 18 and the valve is closed. It is to be noted that the limit abutment 17u engages the switch 18 already before the spring seat reaches the abutment 35. This opening and closing of the valve and the resulting reciprocating movements of the piston are perpetually repeated.

If a foreign body is carried around by the matrix and when passing the sealing plate flank forces this plate away from the end surfaces on the matrix the coupling rods 11 and 11 are moved apart and the spring 15 is compressed. The adjusting device then functions in the following way.

The degree of compression of the spring 15 is dependent on the height of the foreign body and one or several cams 17, 17" etc. slide across the switch 18. Due to the upward movement of the spring seat 14 the piston 33 is released from the spring pressure and the oil pressure in the chamber below the piston 33 and in the supply conduit 31 decreases towards zero. The pressure switch 36 responds to the decreased pressure and opens the valve 37. The piston moves upwardly until the next cam, for instance cam 17, engages the switch 18 so that the valve 37 is again closed. The oil trapped in the lower chamber of the cylinder 30 holds the piston 33 in its raised position also after that the foreign body has left the region of the sector plate and no longer prevents the sector plate from returning to its normal position. However, due to the leakage the piston 33 moves gradually downwardly in the cylinder 30 under the action of the spring 15 and the sector plates and 5' move towards their normal positions. If the foreign body has been removed the piston 33 continues to move until the cam 17 and the limit abutment l7u have reached their normal operative region relative to the switch 18. During this movement the oil pressure is maintained in the lower cylinder chamber. On the other hand, if the foreign body is still lying on the matrix surface the spring is again compressed and the oil pressure in the lower cylinder chamber decreases towards zero so that the pressure switch 36 opens the valve 37 and the piston moves upwardly until the cam 17" again closes the valve 37. These adjusting movements are repeated until the foreign body has been removed. It is evident that in this manner the clearance between the sector plate and the matrix surfaces is not kept widened for a longer time than is necessary and that the normal small width is automatically reestablished as soon as the disturbance has been eliminated.

FIG. 3 illustrates an adjusting device for axial sealing plates. In contrast to the sector plates which usually are (but not necessarily must be) interconnected in pairs each axial sealing plate must be adjusted separately and therefore the adjusting device is modified accordingly. Thus, the device shown in FIG. 3 is designed for a single plate only and may of course be used also for sector plates in such cases where axially aligned sector plates are not interconnected.

According to FIG. 3 the servo motor cylinder 19 is carried by a stationary part shown as a bracket 20. The piston is connected to one end of a rod 23 the opposite end portion 24 of said rod being provided with cams 25 cooperating with a switch 26. The linkage system consists of levers 21 and 21',

bell cranks 22 and 22' and the rod 23. In this case the reset spring 27 is not located adjacent to the cylinder 19 but at the lever 21 which does not have any influence upon its function.

Also in this embodiment of the invention the sealing plate is automatically moved away from the surface of the matrix at disturbances of the type described and as soon as the disturbing element has passed the plate automatically starts to move towards its normal position which it reaches in a relatively short time.

If the disturbing element is not removed the plate will be subjected to a lifting impulse for each revolution of the matrix. However, since the hydraulic device exerts a lifting force upon the plate the contact pressure between the disturbing element and the plate will be much smaller than would be the case if the outward movement of the plate were counteracted by the full force of the compressed spring.

I claim:

1. In a rotary regenerative air preheater having a substantially cylindrical matrix and duct means for directing separate flows of air and flue gases through said matrix, said matrix and duct means being relatively rotatable, and movable sealing elements (5) to reduce the leakage between relatively moving confronting parts of the matrix and the duct means, a device for adjusting the position of a sealing element (5) comprising:

an adjusting linkage (7-11) coupled to said sealing element an hydraulic servo motor (12) coupled to said adjusting linkage for varying the effective length of said adjusting linkage and adjusting the position of said sealing element (5), said servo motor 12) including a cylinder (30) with a piston (33) therein defining a working chamber having an inlet (31) connected to a pressure fluid source;

a spring (15) coupled as a yielding element to said linkage 7-11) and operatively connected to said piston (33) to bias said piston (33) to normally counteract the hydraulic pressure in said working chamber;

a fluid leakage passage forming a restricted outlet from said chamber to provide a delayed emptying of the chamber when the spring force of spring (15) exceeds the force caused by the pressure in the chamber acting on said piston 33);

first sensing means (17, 18) sensing changes of the effective length of said adjusting linkage;

a valve (37) in said servo motor inlet (31) which is coupled to said first sensing means and opened and closed responsive to said first sensing means; and

second sensing means (36) sensing the hydraulic pressure in the inlet (31) of said servo motor (12), said second sensing means (36) being coupled to said valve (37) for opening said valve (37) independently of said first sensing means (17, 18) when the pressure in said inlet (31) falls below a predetermined value.

2. Apparatus according to claim 1 wherein said fluid leakage path is provided around said piston (33).

3. Apparatus according to claim 1 wherein a bore (28) is provided in said piston (33) to form said fluid leakage path.

4. Apparatus according to claim 1 wherein said first sensing means includes a switch (18) and cam (17) arrangement coupled to said linkage (7-11).

5. Apparatus according to claim 4 wherein said switch (18) is fixed relative to said servo motor (12) and wherein said cam (17) is connected to said linkage (7-11) and operates said switch (18) on movement of said linkage relative to said servo motor (12).

6. Apparatus according to claim 1 wherein said second sensing means includes a pressure operated switch (37) located in said inlet (31).

7. Apparatus according to claim 1 wherein said adjusting linkage 7-1 1) is connected to piston (33) of said servo motor 12).

8. Apparatus according to claim 7 wherein said rotary regenerative air preheater includes a second movable sealing element (5') axially aligned with the first sealing element (5),

end of said common housing (l3).

10. Apparatus according to claim 1 including a stationary bracket (20) on said rotary regenerative air preheater, one end of said linkage being secured to said stationary bracket (20), and the other end of said linkage being connected to said movable sealing element.

11. Apparatus according to claim 10 including separate housings for said cylinder of said servo motor and for said spring. 

1. In a rotary regenerative air preheater having a substantially cylindrical matrix and duct means for directing separate flows of air and flue gases through said matrix, said matrix and duct means being relatively rotatable, and movable sealing elements (5) to reduce the leakage between relatively moving confronting parts of the matrix and the duct means, a device for adjusting the position of a sealing element (5) comprising: an adjusting linkage (7-11) coupled to said sealing element (5); an hydraulic servo motor (12) coupled to said adjusting linkage for varying the effective length of said adjusting linkage and adjusting the position of said sealing element (5), said servo motor (12) including a cylinder (30) with a piston (33) therein defining a working chamber having an inlet (31) connected to a pressure fluid source; a spring (15) coupled as a yielding element to said linkage (711) and operatively connected to said piston (33) to bias said piston (33) to normally Counteract the hydraulic pressure in said working chamber; a fluid leakage passage forming a restricted outlet from said chamber to provide a delayed emptying of the chamber when the spring force of spring (15) exceeds the force caused by the pressure in the chamber acting on said piston (33); first sensing means (17, 18) sensing changes of the effective length of said adjusting linkage; a valve (37) in said servo motor inlet (31) which is coupled to said first sensing means and opened and closed responsive to said first sensing means; and second sensing means (36) sensing the hydraulic pressure in the inlet (31) of said servo motor (12), said second sensing means (36) being coupled to said valve (37) for opening said valve (37) independently of said first sensing means (17, 18) when the pressure in said inlet (31) falls below a predetermined value.
 2. Apparatus according to claim 1 wherein said fluid leakage path is provided around said piston (33).
 3. Apparatus according to claim 1 wherein a bore (28) is provided in said piston (33) to form said fluid leakage path.
 4. Apparatus according to claim 1 wherein said first sensing means includes a switch (18) and cam (17) arrangement coupled to said linkage (7-11).
 5. Apparatus according to claim 4 wherein said switch (18) is fixed relative to said servo motor (12) and wherein said cam (17) is connected to said linkage (7-11) and operates said switch (18) on movement of said linkage relative to said servo motor (12).
 6. Apparatus according to claim 1 wherein said second sensing means includes a pressure operated switch (37) located in said inlet (31).
 7. Apparatus according to claim 1 wherein said adjusting linkage (7-11) is connected to piston (33) of said servo motor (12).
 8. Apparatus according to claim 7 wherein said rotary regenerative air preheater includes a second movable sealing element (5'') axially aligned with the first sealing element (5), and including a second adjusting linkage (7''-11'') coupling said cylinder (30) of said servo motor (12) to said second sealing element (5'').
 9. Apparatus according to claim 8 including a common housing (13) containing said cylinder (30) and said spring (15), a piston rod (34) connected to said piston (33) and extending out of said cylinder (30), said piston rod carrying a spring seat (14), said cylinder (30) being located at one end of said common housing (13) and said spring (15) being in a compressed state between said spring seat (14) and the other end of said common housing (13).
 10. Apparatus according to claim 1 including a stationary bracket (20) on said rotary regenerative air preheater, one end of said linkage being secured to said stationary bracket (20), and the other end of said linkage being connected to said movable sealing element.
 11. Apparatus according to claim 10 including separate housings for said cylinder of said servo motor and for said spring. 